1. doc.: IEEE 802.11-05/0211 Submission March 2005 Richard Williams, Texas Instruments, et alSlide 0 Beamforming should be smooth Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at.http:// ieee802.org/guides/bylaws/sb-bylaws.pdfstuart.kerry@philips.compatcom@ieee.org Date: 2005-03-15 Authors:

2. doc.: IEEE 802.11-05/0211 Submission March 2005 Richard Williams, Texas Instruments, et alSlide 1 Beamforming basics Beamforming is a technique to optimize the use of the channel by altering the signal before transmission Given good channel information it is possible to alter the signal before transmission so that it can be received with the greatest reliability possible To allow arbitrary beamforming the receiver must perform channel estimation by simple division To allow arbitrary beamforming to be received without prior knowledge the receiver must use a certain class of techniques for stream separation A general receiver structure doesn’t allow all types of beamforming but can approach optimal performance without channel knowledge

3. doc.: IEEE 802.11-05/0211 Submission March 2005 Richard Williams, Texas Instruments, et alSlide 2 Why beamforming should be smooth A general receiver can outperform a constrained receiver by 5dB –Prescribing the design of the receiver significantly limits the ability to innovate and differentiate –With a prescribed receiver almost all innovation is in the beamforming device and performance is dependent on the reliability of the channel information A general receiver restricts beamforming techniques to those that produce a smooth transmitted signal –A small class of simplistic beamforming techniques is precluded Preambles can be shortened with smooth beamforming techniques –Preamble length is the only factor that affects throughput for any given MAC –Shorter preambles significantly improve throughput –Short packets will always be disadvantaged by longer preambles

4. doc.: IEEE 802.11-05/0211 Submission March 2005 Richard Williams, Texas Instruments, et alSlide 3 Rate needed to equal throughput of WWiSE 135Mbps An extra 12.8μs of preamble requires data rates > 144 4/9 Mbps with data payloads < 3274 bytes 144 4/9 Mbps 135 Mbps

5. doc.: IEEE 802.11-05/0211 Submission March 2005 Richard Williams, Texas Instruments, et alSlide 4 Rate needed to equal throughput of WWiSE 121.5Mbps An extra 12.8μs of preamble requires data rates > 144 4/9 Mbps with data payloads < 1193 bytes 144 4/9 Mbps 121 ½ Mbps

6. doc.: IEEE 802.11-05/0211 Submission March 2005 Richard Williams, Texas Instruments, et alSlide 5 The burden of increased preamble size 144 4/9 Mbps 121 ½ Mbps 108 Mbps 54 Mbps 81 Mbps 135 Mbps 8dB 6dB

7. doc.: IEEE 802.11-05/0211 Submission March 2005 Richard Williams, Texas Instruments, et alSlide 6 Unrestricted beamforming isn’t worthwhile Unrestricted beamforming dictates a poor receiver design Unrestricted beamforming penalizes all transmissions due to the increased preamble size The increased preamble size required by TGnSync requires huge data payloads to compensate for its inefficiency The WWiSE approach of minimizing preambles by requiring smooth beamforming techniques is the right technical solution